Figure 1 identifies controls, indicators, and input and output ports on the front panel on the Mbox 2.
The Mbox 2 front panel provides the following:
S/PDIF LED
This LED indicates that Mbox 2 is using the S/PDIF inputs as the clock source. See “S/PDIF Digital I/O” on page 32.
USB LED
The USB LED indicates that the Mbox 2 has re-ceived power from its USB connection. Once the USB light is on, audio can pass in or out of the system.
Front Panel Headphone Output
Use the Headphone Output to connect stereo headphones with a 1/4-inch stereo connector.
Headphone Level
The headphone knob adjusts the output level of the Headphone port, which outputs the signal that is routed to Outputs 1–2 in Pro Tools LE, and mirrors the Monitor Output ports.
Figure 1. Mbox 2 front panel
48V Gain USB
S/PDIF
Mono Mix
Headphone
Headphone
Source selector LED
LED
Input 1 Level
Output
Monitor Level (Ratio)
Peak Pad LED
Gain Source selector Input 2
Peak Pad LED
Mic/DI LEDs Mic/DI LEDs Mono 48V
LED LED
Monitor Level
The Monitor knob adjusts the output level of the Monitor Output ports. In Pro Tools, this will be the signal routed to Outputs 1–2.
Mix (Ratio) Control
Mbox 2 gives you the ability to monitor your analog input signals while recording, without the delay incurred by A/D/A converters and host-based processing.
This zero-latency analog monitoring is con-trolled with the Mix knob, which you can use to blend and adjust the monitor ratio between Mbox 2 analog inputs and Pro Tools playback.
The Mix knob has no effect when you are using S/PDIF digital inputs, since it controls the signal before it reaches the A/D converters.
To listen to just the Source input signal, turn the Mix knob fully left to Input. To listen to Pro Tools output only, turn the knob fully right to Playback.
The output from the Mix control is routed directly to the Monitor outputs, and is mirrored in the Headphone and S/PDIF output ports.
This ability to blend and control the relative lev-els of Pro Tools playback and latency-free live analog inputs can be particularly effective when overdubbing.
Mono Switch and LED
The Mono switch sums the input channels to a mono signal (delivering that identical signal to both speakers). This has no effect on Pro Tools playback monitoring, recording, or on the main outputs. Switching your stereo source signal to mono is useful when you are recording a mono input while listening to stereo playback (to hear your playing in both sides), or for checking the phase relationship of stereo inputs. When en-gaged, the Mono LED lights.
Monitoring while Overdubbing
By panning signals to the center or using the Mono switch, as opposed to panning them hard left and right in the Headphone outputs, you can create a more focused monitor mix to help minimize distractions while overdubbing.
In situations where you are monitoring stereo microphones, stereo synthesizers, or any source pairs with a comfortable balance, you will prob-ably not want to use the Mono switch.
Checking Phase Relationships
The Mono switch can also be used for a quick check of the phase relationship between Source 1 and Source 2 inputs.
When the two input signals are out of phase, pressing the Mono switch will result in a sudden
“hollow” sound that is the result of phase can-cellation. This quick test with the Mono switch can help to avoid phase problems later when mixing these tracks. Frequent checking of phase relationships with the Mono switch can also as-sist you in finding the optimal microphone placement.
Chapter 5: Mbox 2 Hardware Overview 31
48V Switch and LED
Phantom power is activated by the switch la-beled 48V on the front panel of Mbox 2. The LED, when lit, indicates that 48V phantom power is active on the Mic/Line inputs. These in-puts provide phantom power for microphones that require it to operate.
About Phantom Power
Dynamic microphones (such as a Shure SM57) do not require phantom power to operate, but are not harmed by it. Most condenser micro-phones (like an AKG C3000) do require phan-tom power to operate.
If you are not sure about the phantom power re-quirements for your microphone, consult your microphone’s documentation or contact the manufacturer.
Peak LEDs
These LEDs are clip indicators. If the Peak LEDs flicker occasionally, the signal reaching Mbox 2 has clipped.
Gain Controls
These knobs adjust the input gain levels of the Mic/Line inputs.
Pad Switches and LEDs
The Pad switches engage a –20 dB pad on their corresponding input channels. When engaged, the Pad LEDs light.
Mic/DI Source Selectors and LEDs
These switches select either the Mic (XLR) and Line (TRS) inputs or DI inputs for each channel.
The Mic and DI LEDs indicate the current source input.
Removable Handle
Mbox 2 includes a handle that can be used for carrying and tilting, as well as a replacement panel that makes the unit more compact.
The handle can be used as a stand that tilts the unit into a more easily viewable angle when the Mbox 2 is placed on a desktop. The handle can also be used to carry the unit.
The handle can also be replaced with the op-tional Mbox 2 faceplate panel. This panel lets Mbox 2 sit flat on a desktop, and reduces the space required when packed for traveling.
To replace the handle with the Mbox 2 panel:
1 Unscrew the handle mounting screw located along the right edge of the handle (when view-ing from the front).
2 Remove the handle.
3 Mount the replacement panel in position where the handle had been.
4 Secure the panel to the unit in its new position using the same screw you removed in step 1.
5 Repeat the above basic instructions to replace the panel with the handle.
Although phantom power can be used safely with most microphones, it is possible to damage some ribbon microphones with it. Always turn off phantom power and wait at least ten seconds before connecting or dis-connecting a ribbon microphone.
When using phantom power, Mbox 2’s maximum current per microphone is 4 mA.